In many fields of technology, it is desirable to use robots with an autonomous behaviour such that they can freely move around a space without colliding with possible objects and obstacles.
Robotic vacuum cleaners or robotic floor mops, further referred to as robotic cleaning devices, are known in the art and usually equipped with drive means in the form of one or more motors for moving the cleaner across a surface to be cleaned. The robotic cleaning devices may further be equipped with intelligence in the form of microprocessor(s) and navigation means for causing an autonomous behaviour such that the robotic vacuum cleaners can freely move around and clean a space in the form of e.g. a room. Thus, these prior art robotic vacuum cleaners have the capability of more or less autonomously vacuum clean or mop a room, in which furniture such as tables, chairs and other objects such as walls and stairs are located.
There are basically two categories of robotic cleaning devices known in the prior art;—the ones which clean a surface by random motion and the ones which navigate on the surface using various sensor data.
The robotic cleaning devices, which use a random motion also look randomly for the charger. These robotic cleaning devices navigate and clean by principle of contingency. Such robotic cleaning devices may comprise a collision sensor to avoid collisions when cleaning. Typically they comprise means to detect and locate the charger when they happen to pass it or when the charger comes into the field of view. This is obviously not a very efficient way of cleaning and navigating and may in particular not work very well for large surfaces or for complicated layouts.
The other type of prior art robotic cleaning devices, which navigate using sensor data deduce from the sensor data where they can safely drive without colliding with objects or obstacles. As they make assumptions about their environment based on the sensor data, which is in most cases not complete, they run a high risk of getting stuck or lost. In addition, extracting data and thus making assumptions from the sensor data additionally requires expensive electronic components.
In some cases prior art robotic cleaning devices use a stroke method to clean, which means they drive back and forth stroke by stroke in order to clean a surface. When navigating such a prior robotic cleaning device from one room to another or back to the charger, the robotic cleaning device uses sensor data to navigate. The risk of collision with objects or obstacles is then comparably high, since such robotic cleaning devices are also forced to make assumptions based on the sensor data. This may slow down the robotic cleaning device and thus reduce the efficiency of the cleaning. Additionally a stroke by stroke method may leave a substantial amount of debris or dust remaining, for example close to edges of objects or obstacles. The cleaning may not be neat.
Some known robotic cleaning devices may comprise a side brush arranged close to or at a left or right periphery of a cleaning opening in order to brush debris and dust into and in front of the cleaning opening. When a side brush, in particular only one side brush, is installed on the robotic cleaning device, the cleaning pattern needs to be adapted accordingly to make sure that the side brush is removing the debris and dust in an optimal way.